uva 10114 - Loansome Car Buyer

#include<bits/stdc++.h>

using namespace std;

int main() {

int d,d_n,m,re;

double d_p, l,dp[101],d1,l_d,c_l;

while (cin >> d >> d_p >> l >> d_n && d>=0) {

re=l_d=c_l=0;

while (d_n--) {

cin >> m >> d1;

for ( int i = m ; i < 101 ; i++ )

dp[i] = d1;

}

l_d = l / d,c_l = (d_p + l) * (1 - dp[0]);

while (c_l < l)

re++,l -= l_d,c_l = c_l * (1 - dp[re]);

if (re == 1) cout << "1 month" << endl;

else cout << re << " months" << endl;

}

return 0;

  }