Can anyone help me with test 4?

#include <iostream>
#include <cstdio>

using namespace std;

int main() {
    char c[3];
    float v[3];
    float R = 8.314, p, V, T, n;
    scanf("%c = %f\n", &c[0], &v[0]);
    scanf("%c = %f\n", &c[1], &v[1]);
    scanf("%c = %f", &c[2], &v[2]);
    for(int i = 0; i < 3; i++) {
        if(c[i] == 'p') p = v[i];
        else if(c[i] == 'V') V = v[i];
        else if(c[i] == 'T') T = v[i];
        else if(c[i] == 'n') n = v[i];
    }
    if(c[0] != 'n' && c[1] != 'n' && c[2] != 'n') {
        n = p*V/(R*T);
        if(T == 0 && (p == 0 || V == 0)) cout << "undefined\n";
        else if(T == 0 && (p != 0 || V != 0)) cout << "error\n";
        else if(p < 0 || V < 0 || T < 0 || n < 0) cout << "error\n";
        else printf("n = %f\n", n);
    }
    else if(c[0] != 'T' && c[1] != 'T' && c[2] != 'T') {
        T = p*V/(R*n);
        if(n == 0 && (p == 0 || V == 0)) cout << "undefined\n";
        else if(n == 0 && (p != 0 || V != 0)) cout << "error\n";
        else if(p < 0 || V < 0 || n < 0 || T < 0) cout << "error\n";
        else printf("T = %f\n", T);
    }
    else if(c[0] != 'V' && c[1] != 'V' && c[2] != 'V') {
        V = n*T*R/p;
        if(p == 0 && (T == 0 || n == 0)) cout << "undefined\n";
        else if(p == 0 && (T != 0 || n != 0)) cout << "error\n";
        else if(p < 0 || T < 0 || n < 0 || V < 0) cout << "error\n";
        else printf("V = %f\n", V);
    }
    else if(c[0] != 'p' && c[1] != 'p' && c[2] != 'p') {
        p = n*T*R/V;
        if(T == 0 && (n == 0 || V == 0)) cout << "undefined\n";
        else if(T == 0 && (n != 0 || V != 0)) cout << "error\n";
        else if(V < 0 || n < 0 || T < 0) cout << "error\n";
        else printf("p = %f\n", p);
    }
    return 0;
}